The deterioration of coffee, i.e. the loss of a "fresh" or palatable flavor and aroma, is primarily caused by oxidation and evaporation. In a conventional 8-12 cup coffee receptacle, deterioration is generally so complete within one or two hours, depending on the rate of consumption, as to render the remaining coffee undrinkable.
The role of oxidation, alone, in deteriorating coffee flavor is obvious to anyone who drinks coffee from a sealed container. When the container is first opened, whether after one or several hours, the coffee tastes perfectly fresh. If the container is resealed with a small amount of coffee remaining therein, such as a half a cup, it rapidly deteriorates as evidenced by the poor taste when it is consumed, say, one hour later. There was obviously no significant evaporation from the sealed container but fresh air was admitted at the time the first cup was poured.
The deteriorating role of evaporation is even more obvious as the coffee solution is concentrated by evaporation.
The concept of extending the "pot life" of coffee, i.e. that time period during which it retains the flavor and aroma of freshly brewed coffee, by substantially eliminating its exposure to atmoshpere while yet retaining the ability to pour coffee in conventional fashion was introduced by applicant's prior U.S. Pat. No. 3,974,758. In a pour type coffee receptacle, the patented concept involves sealing the main body of contained coffee with respect to atmosphere. The top of the receptacle is sealed by a movable follower, such as a bellows or bag, and that coffee contained within the lower end of a small diameter pour spout opening into the coffee receptacle adjacent the bottom thereof serves as a liquid seal between atmosphere and the main body of the receptacle contained coffee.
The result is that the only oxidation that can occur takes place at the upper coffee level in the pour spout. By keeping the cross section of the pour spout sufficiently small, that quantity of coffee that is oxidized and subsequently finds its way through the liquid seal to the main reservoir of contained coffee is negligible over the first 4-8 hours depending upon the cross section of the pour spout. Similarly, the only loss to atmosphere that can occur by way of evaporation is at the small uppwer coffee level in the pour spout since a state of equilibrium inherently exists across a gas/vaporizable liquid interface in a sealed container.
Stated differently, the patented concept involves pouring from the bottom of the pot while keeping the top of the pot sealed with a movable follower maintaining atmospheric pressure on the coffee so that it can be poured without creating a vacuum lock.
Previously, the pour spout for "pouring from the bottom" of the pot has been formed externally of the pot as illustrated in applicant's prior patent. This, of course, requires special tooling since conventional coffee pots are not made with small cross section pour spouts opening into the lower portion of the pot.
The purposes of the present invention are; to eliminate the need for a movable follower while yet retaining the advantages of the patented concept, to adapt the same for use with conventionally manufactured coffee receptacles such as those glass decanters used with automatic drip coffee makers and, implicit in the latter, to contain the necessary structure within the height and circumferential profiles of the coffee receptacle with which it is to be used to insure a dimensional match with the particular coffee maker for which the receptacle is sized.